In recent years, systems that use radio frequency identification (hereinafter abbreviated RFID) technology have come into wide use in such applications as inventory management and logistics management. An RFID system includes a reader/writer and a wireless tag attached to each article or the like to be managed, and wireless communications are performed between the reader/writer and the wireless tag. The reader/writer is capable of identifying each individual wireless tag by reading the identification information, etc. stored on the wireless tag. The system can thus manage each individual article to which such a wireless tag is attached.
Japanese Laid-open Patent Publication No. 2006-125650 discloses that a wireless tag is attached to the inside of a metal capsule of a blasting cap to be managed, in order to prevent the wireless tag from being removed and to provide a waterproof structure, and that a lead wire brought outside the metal capsule is used as a monopole antenna.